T1D patients have more CAC than nondiabetic controls but they also appear to have more impaired coronary vasoreactive function. Impaired response to acetylcholine testing and adenosine vasodilation are reported in diabetic subjects. The relationship between coronary microvascular dysfunction and diabetic cardiomyopathy is supported by observation of similar microvascular abnormalities. Endothelial dysfunction not only precedes and predicts clinical macrovascular disease, but also is an independent prognostic marker of adverse long-term cardiovascular outcomes. Significantly greater CAC in T1D was also noted than in non-DM subjects. There is also a greater rate of increase noted in the CACTI cohort.